1. Field of the Invention
The present invention relates to an AC (alternating current) voltage direct-coupled type LED driving apparatus, and more particularly, to a free voltage LED driving device with a high luminous uniformity ratio, capable of driving with a high luminous uniformity ratio by detecting when an external supply AC voltage changes in an LED lighting apparatus to vary and adjust a resistance value so that power is output in a constant manner regardless of the different AC rated voltage of each country.
2. Description of the Related Art
Conventional general lighting apparatuses have incandescent lamps that generate light due to high temperatures, and fluorescent lamps that generate light by high voltage discharges. Since they operate at a high temperature and a high voltage, they do not last very long.
Recently developed LEDs have a long life due to light generated by electron-hole pairs in a semiconductor as the current flows and operating at a low voltage and a low current.
Methods of constant voltage and constant current are commonly used in order to drive such LEDs.
Among these, the constant current driving method is widely used, and a voltage of an LED array is usually driven to 48V or less.
Therefore, a transformer is mainly used to obtain a low voltage from a high AC voltage power source of about 100V to 277V.
If a low-frequency AC power source is applied to a transformer as it is, the transformer must be very large, so switching is performed to change to a high frequency and a relatively small transformer is used.
At this time, noise due to high frequency, harmonics, power factor control and the like are difficult to realize, and so a very complicated circuit is implemented.
For this reason, the price is high, the reliability is low, and the life span is short, causing problems of having to repair or replace within several years.
In recent years, an AC voltage direct-coupled type LED driving method capable of solving these problems has been implemented in a compact, economical, and highly reliable manner and is widely used.
However, there are many points to be improved in the function of the AC voltage direct-coupled type LED driving method.
In general, an AC voltage direct-coupled type LED driving device is configured to have an AC power source, a rectifier, an LED, a switching device, and a current control resistance.
The power is controlled by the current control resistance.
As the magnitude of the current control resistance increases, the power decreases, and as the magnitude of the current control resistance decreases, the power increases.
There are three types of switching devices for configuring such an AC direct-coupled type LED driving device according to a connection method with the LED, that is, a series type, the parallel type, and the current drain type.
The first type of switching device, the series type switching device, is connected in series to the (−) terminal of the LED array. When the switch is on, the LED is lit, and when the switch is off, the LED is off.
The second type of switching device, the parallel type switching device, is connected in parallel at both ends of the LED array. When the switch is on, the LED is turned off, and when the switch is off, the LED is lit.
At a state where the AC voltage is lower than the voltage of the first LED array, the LED is turned off.
When the AC voltage becomes higher than the voltage of the first LED array, the LED is lit.
When the AC voltage is higher than the sum of the first and second LED array voltages, the first and second LED arrays are lit.
As the AC voltage further increases, the LED arrays are lit sequentially.
As described above, when the series and parallel type switching devices are arranged corresponding to a number of LED arrays by a general method, there is a problem that they are sequentially turned on.
In order to solve this problem, switching devices may be appropriately added and arranged in a number more than the LED arrays to make it possible for all LED arrays to be lit simultaneously at an AC voltage higher than or equal to the LED array voltage.
Such a simultaneous lighting method has a very good luminous uniformity ratio characteristic upon dimming.
In such a simultaneous lighting method, there are cases where only a parallel type switching device is used and a case where a parallel type and a series type switching device are used in combination.
However, in the case of using a series type switching device, operation is possible even when a current control resistance is arranged only in one place, but when a parallel type switching device is used, a current control resistance should be arranged for each switching device.
In order to solve the problem of arranging current control resistances in various places, there is a third type switching device, a current drain switching device.
A current drain switching device is a device that has a function of sensing when a current of an LED array flows to its corresponding series type switching device to allow a desired drain current to flow from a (+) terminal of an LED array to a (+) terminal of a next LED array.
By using this current drain switching device, it is possible to divert the current to each LED array to be proportional to the current controlled by the series switching device by a resistance arranged for controlling the current of the series switching device.
However, when the AC voltage fluctuates or the voltage differs for each country or region, the device must be newly designed and manufactured considering the voltage.
Since more than two voltages are usually used in each country, two or more products with different rated voltages are required.
The typical AC voltage range for each country is in the range of 100V to 277V.
However, when installing a LED light emitting device, an electronic device, or electric equipment using a TRIAC dimmer or a 0-10V dimmer equipped with an LED, there is the risk of safety problems such as overheating, destruction, fire and the like due to malfunctioning.
As prior arts, there is (Patent Document 1) KR 10-1217063 B1.